Breast Cancer Overdiagnosis With Screening Mammography

Zahl et al's study in four Norwegian counties suggests that some of the occult invasive breast cancers detected by mammography screening might ultimately have undergone spontaneous regression (1).Population-based statistics in the United States support this hypothesis as well (2).Indeed, since the advent of mammography screening, age-specific breast cancer incidence rates in Europe have increased dramatically among women in those age groups targeted for screening (3).For example, in many western European countries, systematic screening programs were introduced in the late 1980s and early 1990s for women aged 50-69, and this was followed by sharp increases in the incidence of invasive breast cancer in these women (3).This trend is also observed in the United States, as illustrated in figure 1, using data from the Connecticut Historical database of the National Cancer Institute's Surveillance, Epidemiology, End Results (SEER, http://seer.cancer.gov/)program.This figure shows that, since the late 1970s, with increasing utilization of mammography screening among women aged 40-80, age-specific incidence rates for this age group have increased from their baseline rate during 1966 to 1975.